Human inflammatory bowel disease (IBD) includes Crohn's disease and ulcerative colitis. Ulcerative colitis is a chronic disease of the colon, or large intestine. The disease is marked by inflammation and ulceration of the colon mucosa, or innermost lining. The inflammation usually begins in the rectum and lower colon, but it may also involve the entire colon, extending up the colon in a continuous manner. In contrast, Crohn's disease can affect any area of the gastrointestinal tract, including the small intestine and colon, is generally non-continuous, and can affect the entire thickness of the bowel wall.
Both Crohn's disease and ulcerative colitis are believed to be due to an abnormal mucosal T cell responsiveness to bacterial antigens in the gut lumen (Sartor, 1995). In people with IBD, the immune system reacts inappropriately, mistaking food, bacteria, and other materials in the intestine for foreign or invading substances. In the process, the body sends white blood cells into the lining of the intestines, where they produce chronic inflammation. These cells then generate harmful products that ultimately lead to ulcerations and bowel injury. When this happens, the patient experiences the symptoms of IBD.
It is estimated that as many as one million Americans have IBD—with that number evenly split between Crohn's disease and ulcerative colitis. Currently, there is no medical cure for IBD, however, current medical treatments are aimed at suppressing the abnormal inflammation in the colon lining and thereby controlling the symptoms. The major classes of medication that are currently used to treat IBD include aminosalicylates, corticosteroids, and immunomodulatory medicines. However, aminosalicylates are only effective in treating mild to moderate episodes of ulcerative colitis, steroids are not recommended for long-term use due to side effects, and the current immunomodulatory medications (e.g., Azathioprine, 6-mercaptopurine, and methotrexate) can take as long as three months before their beneficial effects begin to work. New and improved medical treatments are therefore needed to treat and prevent the symptoms of IBD.